Gas emission amount is affected by coal seam bury, mining method, coal seam angle and gas content and other geological factors, some of them are known and some are unknown. The mining working face gas emission was taken as grey system. Combined with the prediction features of grey system, less data was collected to predict the gas emission amount of No. 12 coal seam mining of Linxi Mine. According to the grey model theory, the No. 12 coal seam was modeled by grey theory. The result showed that the average accuracy of grey theory was 96.08%, better than the traditional mine statistical method with 91.4% average accuracy, the technology is not limited by geological factors so much, which is superior to the traditional one, with good prospect.